Artificial thread and method for preparing same



-l MOESTURE June 28, 1938. v E. v. LEWIS E AL 2,122,290

ARTIFiCIAL THREAD AND METHOD FOR PREPARING SAME Filed Jan. 2, 1956 FIG. 2

4 HouR CYCLE PROBABLE AVERAGE GRAD- IENT- START Or THROWLNG.

INVENTORS. '0 so 40 so a0 I00 EM Lew/5 d .5. w. Brainar lo 0F CAKE BY WEIGHT BY 72 Insm: To OuTam-z $5M ATTORN Patented June 28, 1938 ARTIFICIAL PATENT OFFICE THREAD AND METHOD FOR PREPARING SAME Everett Vernon Lewis, Richmond, Va., and Seymour Wilson Brainard, Buffalo, N. Y., assignors,

by mesne assignments, to E. mours & Company; Wilmington,

poration of Delaware I. du Pont de Ne- Del., a cor- Application January 2, 1936, Serial No. 57,074

6 Claims.

The present invention relates to the production of artificial threads and filaments, and more particularly it relates to an improved process and means for the production of artificial threads and filaments having substantially uniform physical characteristics throughout the lengths thereof.

This invention will be described with particular reference to the production of regenerated cellulose threads and filaments made from viscose by the bobbin process. It is to be understood, how'- ever, that the invention is'generally applicable to the production of artificial threads and filaments by the bobbin process from other cellulosic solutions, for example, from cuprammonium cellulose solution or from solutions of lowly etherified or lowly esterified cellulose.

In the bobbin process for the manufacture of regenerated cellulose threads from viscose, the freshly spun yarn is drawn from the coagulating bath and wound on bobbins rotating at a constant peripheral speed as a bundle or band of continuous parallel filaments. wound is saturated with spinning bath and byproducts of its manufacture.

The bobbins are usually perforated to permit subsequent pressure or vacuum liquid treatment of the yarn Wound thereon, since it must be free from acid and certain by-products of its manufacture before it can be used. Inasmuch as the filaments are in parallel relationship and not twisted together, the yarn is not capable of withstanding excessive handling or treatment without deleteriously affecting its quality. Furthermore, the tightness of the cake and non-uniform texture 35' make purification diflicult. It is therefore common practice merely to subject the bobbin of yarn as it comes from the spinning machine to a washing treatment to remove the bath liquor contained in the yarn, after .which the yarn is dried on the bobbin.

The washed and dried yarn is next twisted. For example, according to one method of twisting, the bobbin of dried, untwisted yarn is mounted on a vertical spindle and rotated thereon at severalthousand revolutions per minute while the thread is drawn from the end of the bobbin and wound up on the surface driven, horiz'ontal, take-up bobbin at a constant linear speed. The complete drying of the yarn on the bobbin prior to the twisting operation necessitates its rewinding into skeins for subsequent processing, such as desuliuring, bleaching, washing, and the like, to eliminate the uneven shrinkages which have been set up in the various layers of yarn on the bobbin during the drying thereof.

The yarn so Skein processing of yarn is known to be expensive andobjectionable in view of the degradation of the yarn due to the repeated handling thereof. Furthermore, when the yarn is first dried on the spinning bobbin, inequalities in the shrinkage of the thread which have been set up in the various layers of thread comprising the original spun cake must be removed. These inequalities in the shrinkage ofthe thread on the original spun package are caused by the greater resistance to shrinkage of the inside layers of the thread than the outside layers of the thread. This greater resistance to shrinkage of the inside layers of thread is due to their closeness tothe rigid bobbin upon which they are wound. As a result, when skeins of such yarn are wetted, for instance, during purification, various parts of the yarn comprising the skeins shrink differently with the result that the yarn can be rewound only with difliculty and with serious loss in yarn quality.

In order to avoid the skein treatment of yarn, numerous processes have been proposed for the processing of yarns in package form. It has been proposed, for example to partially dry all the thread on the spinning bobbin until it, contains a given moisture content throughout and then throwing or'twisting the same while still in the gel state, on toa take-up bobbin from which the thread may be removed and processed as unsupported cakes.

In U. S. Patent No. 2,046,347 to George Sigler, there is disclosed a process for throwing of the yarn partially dried toa given moisture content throughout but while it is still in the gel state, or when it has not yet been dried to less than about 50% moisture, based on its dry weight. The yarn is thrown under conditions such that the yarn dries during its travel from the supply bobbin to the wind-up or take-up bobbin and under such conditions as to permit delivery to the take-up bobbin of substantially uniformly shrunk yarn.

It has now been found that the process as disclosed by the above identified patent to Sigler can be further improved by preliminarily drying only the outer layers of the yarn on the spinning bobbin prior to the gel throwing thereof.

In order to produce a uniform yarn suitable for weaving purposes without resorting to skein processing, it is necessary to twist and substantially simultaneously wind the yarn into a soft, pervious package which can subsequently be uniformly treated with purifying solutions and dried without causing non-uniform shrinkage characteristics. The solution of this problem involves a new process of reducing the moisture content of the untwisted yarn on the spinning bobbin so that the outer layers of yarn will have a much smaller moisture content than the inner layers after which it can be handled more effectively in the gel throwing process described by Sigler. Furthermore, it involves the novel method of winding up the thread on the throwing machine so that the package produced is uniformly soft and will readily permit the penetration of various treating solutions and can then be dried under suitable conditions without the yarn shrinking non-uniformly, for example, in the manner disclosed in co-pending application Serial No. 57,075 filed by E. V. Lewis on even date herewith. The above identified application discloses the throwing of this yarn on apparatus which is provided with take-up bobbin mechanism adapted to form a package having a uniform density, which package may be removed from the take-up bobbin for treatment by various liquid purifying solutions.

It is therefore an object of this invention to provide a method and means for producing artificial threads and filaments having improved shrinkage characteristics. It is another object of this invention to provide an improved method and means for preliminarily drying, and simultaneously gel throwing and winding a package of artificial threads or filaments, in which the package may be subjected to various liquid purification treatments without affecting the uniform shrinkage characteristics thereof.

It is the more specific object of this invention to preliminarily dry the outer layers of freshly spun artificial thread on a spinning bobbin, throwingthe thread from the spinning bobbin and winding the same on to a take-up bobbin in a manner to form a removable yarn package which is suitable for liquid purification treatment, whereby to obtain a yarn having uniform shrinkage characteristics. invention will appear hereinafter.

The objects of the invention may be accomplished in general, by subjecting bobbins of freshly spun untwisted yarn that have been taken directly from the wash rack to a partial drying step in which the outer layers of the thread are dried to a much greater extent than the inner layers thereof prior to the liquid purification treatment of the yarn.

It is desired that the very outside layers of the yarn after the preliminary drying thereof contain about 20% to 30% moisture, based on the dry weight of the thread, at the beginning of the throwing step. Since it takes from 10 to 20 hours to complete the unwinding of one cake of yarn from the spinning bobbin which is being rotated at from 2000 to5000 R. P. M., substantial drying out of the yarn comprising the inner windings takes place in situ as the yarn is rotated and as it balloons from the throwing spindle. It is therefore important that the gel throwing of the thread is carried out with the inner windings of yarn on the spinning bobbin having sufficiently greater moisture content than the outer windings at the beginning of the winding operation so that when the inner windings of the thread are drawn from the spinning bobbin, they will not already have dried and shrunk against the rigid bobbin, or the compact layers of thread underneath. The drying of the cake should therefore be carried out so that the cake has a moisture gradient from the outside to the inside rang- Other objects of the I 'as for example by means of bolts 21.

ing from about 20% on the extreme outside to about 160% on the inside, based on the dry weight of the yarn. The moisture gradient may vary somewhat from the figures just given. For example, the thread on the outside of the spinning cake may have a moisture content ranging from 20% to 60% while the moisture content of the thread comprising the inner half of the cake may range from to 175% and preferably to based on the dry weight of the yarn. In order to obtain this type of moisture gradient, it is necessary to dry the yarn from the outside of the cake and prevent as much as possible any drying from the inside thereof. It is therefore desirable to plug the bobbin end to retard drying from the inside thereof.

The details of the invention will be more clearly apparent by reference to the following detailed description taken in connection with the accompanying illustration in which:

Figure 1 is a vertical sectional view of a spinning bobbin positioned in a drying apparatus for drying of the outer layers of yarn in accordance with the present invention.

Figure 2 is a graphic illustration showing the moisture gradients of the various sections of the cake from the inside to the outside after being subjected to a preliminary partial drying operation in accordance with the present invention.

Referring to the drawing reference numeral I l designates one of the main supporting members of the drying apparatus containing a plurality of openings M for the passage of drying air and containing imperforate portions on which holding members I2 are fixedly positioned and upon which spinning bobbins may be mounted. The holding member I2 may be connected to the imperforated portions of the support II in any desired manner, such as for example by means of bolts l3. The holding member [2 is comprised of a base IS, a rubber gasket l1, and a spacing member IS. The bobbin I9 containing the thread 2| is forced over the member 16 until it engages the rubber gasket H, which will cause it to be firmly positioned on the support of the drying apparatus. A plug 23 is inserted in the other end of the bobbin l9 to prevent the circulation of any air on the inside of the bobbin. The plug 23 comprises a base portion 25 and a spacing member 26 which latter two elements are fixedly connected to each other in any desired manner, such It is preferred that the plug member 23 be provided with a rubber gasket 26 which will engage the top of the bobbin 19 when the plug is in position therein.

As one specific example illustrating the operation of this invention, a spinning bobbin cake containing about 0.4 lb. of 100 denier-40 filament yarn having a moisture content of about 225% based on the dry weight of the yarn, is subjected to a partial drying operation for 4 hours in a drying chamber, heated to about 130 F. and maintained at a relative humidity of about 15% to 20%. The bobbins of yarn before they are charged in the dryer are plugged in the manner indicated above and air is passed by the cake in the'manner shown by the ar rows in Figure 1 of the drawing. The velocity of the air may vary and is adjusted in such a manner that the moisture gradient of the cake so dried will be approximately in accordance with the curve designated by A in the Figure 2 of the drawing.

It is to be understood, of course, that if the yarn package contains a greater or smaller amount of yarn, or is of different denier, the time of drying and the temperature and humidity of the dryer may be varied accordingly. The drying operation may, for example, be conducted with the temperature of the drying air ranging between 1151 F. and 150 F., with the relative humidity in the dryer ranging from to 30%, and with the velocity of the air ranging between 100 to 1000 feet per minute. It

is important that the moisture gradient be in general that shown by the curve A although a considerable variation in the curve in the inner 80% of the cake can be tolerated without defeating the purpose of this invention. It is important, however, that the outer 10% of the cake be dried to at least about 60% moisture content and not less than about 20% moisture content based on the dry weight of the yarn.

By drying the yarn in the manner described, the process of gel throwing such as is described in the Sigler patent above referred to can be carried out most effectively. The throwing step, which is preferably carried out in the presence of substantially constant temperature and humidity conditions, may last up to 20 hours, usually about 15 hours, and during this time considerable drying out of the yarn takes place, especially if the room humidity is maintained at a value low enough to dry the yarn down to about 20% moisture in its travel from the throwing bobbin to the take-up bobbin. The moisture gradient obtained in the drying procedure described operates to eliminate the drying of the inner windings of yarn to a point where substantial shrinkage would tend to take place and set up internal strain in these yarn layers. This improvement permits the unwinding of yarn from the spinning bobbin with the yarn being removed at more uniform conditions of moisture content, and the yarn wound on the take-up bobbin will possess somewhat more uniform shrinkage characteristics than was possible by the process described in the aforementioned Sigler application.

Yarn processed in accordance with the present invention has been found to possess great uniformity in the moisture content thereof in the package which is subsequently to be submitted to liquid treatment by reason-of the fact that the cakes have not been dried substantially below 20% moisture content. The yarn is more readily acted upon by desulfuring and bleaching solutions than when the yarn has been dried substantially below equilibrium with moisture in the air and allowed toregain a moisture content and thus permits substantially complete sulfur removal and uniform bleaching of the yarn without deleteriously affecting the same.

Obviously many changes and modifications can be made in the above detailed description without departing from the nature and spirit of the tificial thread on a bobbin, the steps comprising drying the thread on said bobbin, by means of heated circulating gases applied solely from the exterior surface thereof, and stopping said drying when the moisture content of the outer layers of the thread on said bobbin has been lowered to between 20 and 60%, while at the same time the moisture content of the inner layers thereof is above 60%. 1

2. In a, method of processing freshly spun artificial thread on a bobbin, the steps comprising drying the thread on said bobbin, by means of heated circulating gases applied solely from the exterior surface thereof, and stopping said drying when the moisture content of the outer layers of the thread onsaid bobbin has been lowered to between 20 and 60%, while at the same time the moisture content of the inner layers thereof is above 60%, then drying and twisting said thread during its removal from said bobbin.

3. In a method of processing artificial thread, the steps comprising drying freshly formed artificial thread wound on a spinning bobbin, by means of heated circulating gases applied solely from the exterior surface thereof until the outer layers of yarn have a moisture content of between 20 and 60%, while at the same time the moisture content of the inner layers thereof is above 60%, then twisting said yarn during its removal from said bobbin.

4. In a method of processing a freshly spun artificial thread package, the steps comprising drying said package by means of heated circulating gases directed solely against the exterior surface of said package, and stopping said drying when the moisture content of the outer layers of thread on said package has been lowered to between 20 and 60%, .while at the same time the moisture content of the inner layers thereof is above 60%, then drying and twisting said thread during its removal from said package.

5. In a method of processing a freshly spun artificial thread package, the steps comprising drying said package by means of heated circulating gases directed solely against the exterior surface of said package, in such a manner as to' obtain a package having a moisture content of 20 to 60% in the outer layers thereof, and a moisture content of to in the inner half of said package, then drying and twisting said thread during its removal from said package.

6. In a method of processing a freshly spun artificial thread package, the steps comprising drying said package by means of heated circulating gases having a relative humidity of 15 to 20%, directed solely against the exterior surface of said package in such a manner as to obtain a package having a moisture content of 20 to 60% in the outer layers thereof, and a moisture content of 100 to 175% in the inner half of said package, then drying and twisting said thread during its removal from said package.

EVERETT VERNON LEWIS. SEYMOUR WILSON BRAINARD. 

